Meaning
Pressure vessels containing compressible gas charges that store fluid energy and dampen pressure surges fulfill auxiliary power functions in industrial fluid systems. Compressed nitrogen gas behind a flexible bladder or piston compresses when hydraulic fluid enters under system pressure. Plant engineers incorporate pneumatic accumulator units to maintain circuit pressure during pump outages and absorb fluid hammer.
The scope excludes unpressurized venting reservoirs open to ambient atmospheric conditions.
Energy Storage
Hydraulic fluid forced into the shell compresses the internal pre-charge gas volume according to gas laws. Stored fluid returns to the system instantly when line pressure drops below accumulator gas pressure. Hydrostatic pressure testing verifies pneumatic accumulator integrity up to maximum allowable working pressure ratings before commissioning.
Neglecting pre-charge pressure checks leads to bladder rupture or complete loss of reserve hydraulic volume.
Surge Dampening
Rapid valve closures generate high-amplitude shock waves that propagate along rigid fluid piping lines. Nitrogen gas cushions absorb transient energy peaks to prevent pipe displacement and seal failure. Accumulators installed near fast-acting valves reduce peak shock pressure magnitudes.
Precharge Boundary
Correct gas pre-charge pressures ensure maximum fluid volume displacement during emergency operating cycles. Excessive nitrogen pressure prevents fluid entry while low pressure causes bladder bottoming. Maintenance protocols mandate periodic pre-charge verification using dry nitrogen gas.
